/**
    * Copyright 2005-2013 The Kuali Foundation
    *
    * Licensed under the Educational Community License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    * http://www.opensource.org/licenses/ecl2.php
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.kuali.rice.kew.validation;
  
  import org.apache.commons.lang.StringUtils;
  import org.kuali.rice.kew.api.WorkflowRuntimeException;
  import org.kuali.rice.kew.api.validation.RuleValidationContext;
  import org.kuali.rice.kew.api.validation.ValidationResults;
  import org.kuali.rice.kew.framework.KewFrameworkServiceLocator;
  import org.kuali.rice.kew.framework.validation.RuleValidationAttributeExporterService;
  import org.kuali.rice.kew.rule.RuleValidationAttribute;
  
  import java.lang.reflect.InvocationHandler;
  import java.lang.reflect.Method;
  import java.lang.reflect.Proxy;
  
  /**
   * RuleValidationAttributeResolver reference impl.  Returns a proxy which delegates to the appropriate
   * RuleValidationExporterService.
   *
   * @see org.kuali.rice.kew.rule.RuleValidationAttribute
   * @see org.kuali.rice.kew.framework.validation.RuleValidationAttributeExporterService
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public class RuleValidationAttributeResolverImpl implements RuleValidationAttributeResolver {
      @Override
      public RuleValidationAttribute resolveRuleValidationAttribute(final String attributeName, String applicationId) throws Exception {
          final RuleValidationAttributeExporterService service = findRuleValidationAttributeExporterService(applicationId);
          return (RuleValidationAttribute) Proxy.newProxyInstance(this.getClass().getClassLoader(), new Class<?>[] { RuleValidationAttribute.class }, new RuleValidationAttributeInvocationHandler() {
              @Override
              protected ValidationResults invokeValidate(RuleValidationContext context) throws Exception {
                  return service.validate(attributeName, context);
              }
          });
      }
  
      protected RuleValidationAttributeExporterService findRuleValidationAttributeExporterService(String applicationId) {
          RuleValidationAttributeExporterService service = KewFrameworkServiceLocator.getRuleValidationAttributeExporterService(applicationId);
          if (service == null) {
              throw new WorkflowRuntimeException("Failed to locate RuleValidationAttributeExporterService for applicationId: " + applicationId);
          }
          return service;
      }
  
      protected static abstract class RuleValidationAttributeInvocationHandler implements InvocationHandler {
          @Override
          public ValidationResults invoke(Object o, Method method, Object[] objects) throws Throwable {
              if (!StringUtils.equals(method.getName(), "validate")) {
                  throw new UnsupportedOperationException("RuleValidationAttribute only supports 'validate'");
              }
              return invokeValidate((RuleValidationContext) objects[0]);
          }
          protected abstract ValidationResults invokeValidate(RuleValidationContext context) throws Exception;
      }
  }